The accurate calculation of transmission line modes is very important for power line design, the dynamic properties, anti-vibration, anti-galloping analysis. However, the existing simplified theories and models will Cause large calculation error. Based on the strain - displacement relationship of spatial curved beam theory, a three-node curved beam power line element was realized, which was used to take a modal analysis. The results show that the curved beam element used to calculate modes of power line is accurate. The results of the analysis were compared with results of only considering translation of power line, results of considering axial deformation and bending. The results of parametric analysis show that the bending cross-section modulus of the transmission lines has a greater impact on the translation and rotation frequency. The iced conductor eccentricity can slightly reduce the frequency of wire.